The present invention relates generally to vehicle supplemental inflatable restraint systems and, more particularly, to an air bag module that provides variable output inflation of an air bag cushion from a single inflator.
Driver side or passenger side supplemental inflatable restraint (SIR) systems typically include an air bag stored in a housing module within the interior of the vehicle in close proximity to either the driver or one or more passengers. SIR systems are designed to actuate upon sudden deceleration so as to rapidly deploy an air bag to restrain the movement of the driver or passengers. During deployment, gas is emitted rapidly from an inflator into the air bag to expand it to a fully inflated state.
Air bag passive restraint systems include an inflator, which produces gas to inflate the air bag cushion. Known inflators for air bag modules are generally of three types. One type is the pure gas inflator wherein a pressure vessel contains stored pressurized gas. The pressure vessel communicates with the cushion through various types of rupturable outlets or diaphragms. Another type is the gas generator wherein a propellant is ignited and the resultant gas created flows through an outlet to the cushion. A third type is the hybrid or augmented type. This type includes a pressure vessel containing stored pressurized gas and a gas generator. When the generator is ignited, the resultant gas flows with and heats the stored gas going to the cushion through the pressure vessel outlet.
It is also known to inflate the cushion at a relatively low rate under low level deployment conditions, such as a sudden low level deceleration, and at a relatively high rate under high level deployment conditions, such as a sudden high level deceleration. Devices are known which provide primary inflation (reduced inflation) and full level inflation using a single gas vessel with two separate gas heaters. Primary inflation is accomplished by actuating the gas vessel and heating the gas at a specified reduced level. Full level inflation is accomplished by actuating a second separate heater located at the bottom of the gas vessel to heat the gas at a greater level. This second heater is deployed at the same time or a delayed time as the primary heater to provide full level inflation. It is also known in the art to use a system having two discrete inflators to accomplish dual level inflation. In these types of systems, two discrete inflators are deployed at the same time or at a delayed time depending upon the severity of the sudden deceleration.
This invention offers advantages and alternatives over the prior art by providing an air bag module which offers variable output inflation of an air bag cushion. The air bag module includes an inflator, a cushion retainer, a slide mechanism, and a base plate for supporting the inflator, the slide mechanism, and the cushion retainer. The cushion retainer includes inner and outer annular walls, wherein the slide mechanism is disposed between the inner and outer annular walls. The cushion retainer includes at least one and preferably a plurality of diffuser openings and the slide mechanism comprises a rotatable ring having openings formed in an annular wall thereof. The slide mechanism has connecting tabs at an upper edge thereof and each connecting tab is connected to a first end of a tether. The second end of the tether is secured to a rear surface of an air bag cushion. The air bag cushion is disposed about the inflator, cushion retainer and base plate, wherein the air bag cushion is retained to the cushion retainer.
Under deployment conditions, a controller actuates the inflator to cause generation of heated inflator gas. The heated inflator gas is discharged through vent ports formed in the inflator and flows initially according to a first fluid flow path in which the heated inflator gas flows into the air bag cushion. As the air bag cushion begins to inflate the rear surface thereof becomes under stress and the second end of each tether attached to the air bag cushion tightens. Because the first end of the tether is attached to the connecting tab of the slide ring, the slide ring is rotated about the cushion retainer as a result of the tightening of the tether. As the slide ring rotates, the openings formed within the slide ring axially align with the openings formed in the cushion retainer. The alignment of the openings effectively opens a second fluid flow path, wherein the heated inflator gas flows through the openings of the cushion retainer and the slide ring and exits the air bag module through an opening formed in the base plate. Thus, some of the heated inflator gas is directed away from the air bag cushion resulting in reduced inflation thereof.
The use of the slide mechanism and attached tethers provides a direct mechanical system for cushion pressure feedback to tailor the inflation. More specifically, the use of tethers in combination with the slide ring permits the pressure of the air bag cushion to be sensed, due to the unfolding action of the air bag cushion, and when the cushion pressure reaches a predetermined level, some of the heated inflator gas is vented off and is directed out the air bag module away from the air bag cushion.
The slide mechanism of the present invention permits the proper variable inflation of the air bag cushion when the occupant is in either a forward position in a seat, a more rearward position in the seat, or positions therebetween. When the occupant is positioned closer to the SIR system, the inflating air bag cushion contacts the occupant earlier in the inflation process than if the occupant was seated more rearwardly in the seat. As the air bag cushion contacts the occupant and continues to inflate, the rear surface of the air bag cushion will become stressed earlier in time than if the occupant was seated more rearwardly. Accordingly, the tether is tightened earlier resulting in the rotation of the slide ring to thereby open the second fluid flow path. This results in some of the inflator gas being directed away from the air bag cushion and therefore a lower level of deployment is achieved. In other words, when the occupant is positioned closer to the SIR system, the actuation of the slide ring occurs sooner in time than if the occupant is seated more rearwardly. When the occupant is seated more rearwardly, the air bag cushion inflates to a greater volume before contacting the occupant. Thus a higher level of deployment is achieved before the air bag cushion becomes stressed and the slide ring is actuated to direct some of the inflator gas away from the air bag cushion. Advantageously, the slide mechanism provides variable inflation and the slide mechanism is designed to actuate depending upon the positioning of the occupant so as to inflate the air bag cushion to a desired predetermined level.
The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.